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In the optimal control of any physical process about its operating point, a requirement of prime importance is the identification of the process parameters. This requires the realisation of both the static and dynamic characteristics of the control system. A method of identifying multi-variable non-linear systems is presented in this paper. The method uses correlation techniques around the tracked operating point of the system. The correlation method uses several uncorrelated maximal length (pseudo-random) sequences of small amplitude as test signals. This facilitates on-line identification during the normal process operation. A further advantage of this method is that a system identification may be made in the presence of noise and other inherent disturbances. The technique is first applied to a multi-variable system containing cubic non-linearities and then to one containing four hysteresis elements. Finally, an identification was made of the non-linear cross-coupling dynamics between the roll and yaw axes of an aircraft.

The implementation of multi-level control schemes for large industrial processes is discussed, with particular emphasis on the problems of data transmission between computers operating at various levels in the system. The operation of one type of inter-processor data link is considered in detail and its relevance as a research facility for hierarchical control systems is demonstrated. Applications which make use of this facility are presented illustrating the diverse data transmission requirements of multi-level systems.

The inaugural Hartley Lecture was given by HRH The Prince Philip, Duke of Edinburgh, KG, KT, OM, at the Wellcome Lecture Hall of The Royal Society, London, on Tuesday, 21 May, 1974. This Lecture was founded in honour of the late Sir Harold Hartley, GCVO, CH, CBE, MC, FRS, jointly by The Institute of Measurement and Control, The Institution of Chemical Engineers and The Royal Society.

A method for continuously measuring the quantity of non-conducting immiscible liquid dispersed in a detergent slurry is developed. The instrument relies on measuring the rms value of fluctuations in the instantaneous resistance across electrodes in the flowing fluid. Fundamental concepts underlying this technique are discussed, together with the details of the measuring system and the construction of the electrodes. Some experimental results are presented which show that the output of the instrument is proportional to the quantity of the dispersed phase. This technique is generally applicable to any two-phase fluid system where the carrier is conducting and the minor discontinuous component has a different value of conductivity.

The paper describes a simple procedure for tuning discrete proportional — integral — derivative control algorithms. Two recommendations which are currently employed to select controller parameters are combined. For a given sampling frequency this leaves only the controller gain to be adjusted on each control loop. The technique has been applied to the regulation of a process represented by a single time constant and time delay which is subjected to load disturbances. Digital simulation results are given which show that acceptable regulation is obtained which is comparable to tuning all three controller parameters to minimise a specified integral performance index.

Part of the instrumentation for measurement of pollution from motor vehicles is described. The methods are selected for sensitivity and selectivity and will give a continuous record. Calibration is important and selected example procedures are described. The data-handling problem is overcome by inclusion of a 10-channel logger with punched paper tape output.

Results are presented showing how the performance of wedge-probes at low Mach number may be affected by the geometry of the front pressure tapping recess in the leading edge and also by the shape of the leading edge.

This work forms part of a study into reflection behaviour within a duct directed towards the understanding of the problems associated with metering pulsating gas flows. A novel application of correlation analysis is used to predict the shape of the reflected wave from an opening of finite thickness. The incident wave is in the form of a pseudo-random binary sequence pressure pulse sequence which enables incident and reflected waves to be distinguished one from the other. It is shown that for waves of small amplitude, reflections do not occur in like shape to that of the incident wave. These shapes are influenced by both the amplitude of the incident wave and the geometry of the opening. It is believed that this technique makes an original contribution to the study of reflection behaviour and the use of correlation analysis.

Low carbon soft iron is used in the manufacture of relays. An instrument is described which can grade the coercive force of such steel with a minimum of sample preparation. Satisfactory correlation is found between results obtained from the grader described and classical testing methods.

The convention began with an introductory talk by Prof J. H. Westcott of Imperial College, who highlighted the immense growth of emphasis towards control engineering. He described briefly a few of his own projects including a model of the national economy designed to yield a greater understanding of the major controllable variables influencing the behaviour of the system. Following this introduction, the Pro- Vice Chancellor of the University of Bath, Prof Austwick, welcomed the delegates and The Institute to the University.

The paper discusses the programme of space exploration to be undertaken by the Space Shuttle Transportation System which is currently being developed by NASA. The basic parameters of Space Shuttle are identified and the major subsystems contributing to the shuttle are reviewed. The instrumentation-needs, and the constraints applying to it, are addressed; the paper concluding with a brief reference to the potentials of technical spin-off from this momentous programme.

The report describes a digital simulation study of the application of discrete prediction filters, designed from Taylor series expansion or the method of least squares, to direct digital control, where the prediction filter is inserted in the feedback path. The effects on system performance to set-point changes and load disturbances are investigated. In addition, the effects of process noise and system stability are considered. It is concluded that accuracy of prediction is not the most important property which affects control performance. Best performance is obtained using a filter which has a low sensitivity to process noise and predicts as far as possible into the future while remaining within stability constraints.

This paper outlines modern optimal control theory and its possible application to the design of some aircraft control systems. Both continuous and discrete control laws are considered. Deterministic linear systems with a quadratic index of performance (state feedback) are discussed and extended to real and implicit model-following. Output feedback control laws are introduced using gain matrices and state observers, leading to the (Stochastic) Kalman-Bucy filter. The effects of plant parameter variation with flight condition are related to the design of ‘desensitised’ control laws. Comment is also made on suitable state variable models.

In this paper, the effect of the method of control on the transfer function of two-phase servomotors is investigated. The methods of control considered are the amplitude, time-phase, frequency, voltage-frequency, pulse-width and space-phase control. Torque equations are derived for different methods. The motor gain and time-constant are determined from the torque-speed and speed-signal characteristics. The servomotor torque, speed, time-constant and gain — and their dependence on the signal magnitude — are compared for the different methods of control. It is shown that for the same value of the signal, the motor time-constant may vary between 2·2 msec and 45 msec and the gain may be increased six times if the method of control is changed.

An improved method of reference model adaptive control is developed which provides fast adaptation of system parameters. Application of the theory is demonstrated on a practical example with three adaptive variables.